The present invention relates generally to the field of audiometric devices and associated screening methods. More particularly, the invention relates to an acoustic coupling device for use in connection with equipment for stimulating the reaction to sound in a subject.
Language acquisition in infants requires a critical period of hearing capacity, which spans the frequency range of human speech. The critical period extends from birth to about two to three years of age, when infants typically begin to talk with some level of proficiency.
Various hearing screening techniques have been developed over the years which present a sound input into the ear of a subject (i.e., infant) and detect a response to that input. The response is related to the characteristics of the sound input and the conditions inside the ear, the neural connections, and the vibration transmission mechanism of the ear.
In many instances, hearing screening is performed by using an earphone having a cavity that fits closely about the ear. Auditory tones or xe2x80x9cclicksxe2x80x9d are fed into the earphone cavity, and the response generated by the patient""s ear and the neural conduction system in response to the auditory tones is sensed by a transducer. The transducer may be, for example, a microphone, suitable electrodes, piezo electric materials and like devices that generate signals representative of the response to the auditory input.
There are, however, several problems associated with the noted technique. A major problem is that ambient noises, internal or external to the cavity, are capable of interfering with the stimulus or the response signals and, hence, the results. In most cases, the monitoring equipment has mechanisms, such as microphones, for detecting and compensating for ambient background noise. Illustrative is the disposable earphone disclosed in U.S. Pat. No. 4,930,520 (Liverani), which is sold under the trademark Ear Couplers(copyright) by Natus Medical, Inc.
The Liverani earphone includes a toroidal baffle of anechoic, insulative foam, a clear planar window plastic sheet adhered to one side of the baffle defining a cavity, and an adhesive coating on the other side of the baffle for bonding the disposable earphone to the region surrounding the infant""s ear. The earphone is employed with transducers for transferring acoustical energy through a pneumatic tube to the infant""s ear for testing.
One of the problems with the Liverani device is that the earphone is somewhat cost-ineffective in that the entire earphone is not re-usable and must be disposed of after each use. Another problem with the device is that its construction is not capable of adjustment for infants with different size ears. As a result, it is necessary to manufacture different size earphones and maintain an inventory of the different sizes to obtain acceptable test performance for infants having different sized ears.
A further problem is that the Liverani device does not include any means for regulating or monitoring the amplitude of the stimulus presented to the infant.
In U.S. Pat. No. 5,913,309 a disposable earphone element is disclosed for use in hearing screening tests, which addresses some of the disadvantages associated with the Liverani device. The disposable element similarly includes an adhesive on one side of the element, which is adapted to adhere to the patient""s skin around the ear. An adhesive is further provided on the opposite side of the element to temporarily adhere to the earphone. Thus, after a test is conducted, the disposable element is merely removed and replaced, allowing one to reuse the earphone.
Although the disposable element disclosed in the ""309 eliminates the need to replace the entire earphone after each use, replacement of the disposable element is still somewhat cost-ineffective. Further, the disposable element does not include any means for regulating or monitoring the amplitude of the stimulus.
Finally, a problem associated with each of the noted devices is that the adhesive employed to adhere the devices to the skin is generally ineffective to maintain full contact with the infant during the period of hearing screening. Thus, ambient noise can, and in many instances will, enter into the cavity.
It is therefore an object of the present invention to provide an improved acoustic coupling device that overcomes the problems of prior art devices and, further, provides means for regulating and/or monitoring the amplitude of the stimulus presented to the subject.
In accordance with the above objects and those that will be mentioned and will become apparent below, the acoustic coupling device (or apparatus) in accordance with this invention comprises a coupling input adapted to engage a hearing screening device, the coupling input being adapted to receive an acoustic stimulus from the hearing screening device and transmit at least one response signal from a subject (or patient) to the hearing screening device; a first passive attenuator adapted to attenuate a first frequency of the acoustic stimulus; a second passive attenuator adapted to attenuate a second frequency of the acoustic stimulus, the first and second passive attenuators in combination providing a second acoustic stimulus having a substantially balanced acoustic spectrum; at least a first earpiece disposed proximate the ear canal of one of said subject""s ears, the earpiece including a stimulus input adapted to transmit at least the second acoustic stimulus to the subject and receive at least a first response signal from the subject""s ear, the first response signal having a first volume; and a response signal compensator adapted to regulate the first volume of the first response signal.
The method of testing the hearing of a subject in accordance with the invention comprises the steps of (a) presenting a first acoustic stimulus to a first passive attenuator, the first acoustic stimulus having at least first and second frequencies; (b) passively attenuating the first and second frequencies to yield at least a second acoustic stimulus having a substantially balanced acoustic spectrum; (c) transmitting the second acoustic stimulus to the inner ear of the subject; (d) detecting a first response signal from the subject""s inner ear, the first response signal having a first volume; (e) regulating the first volume to a pre-selected second volume; and (f) detecting the first response signal having the second volume.